#canvas {
    display: block;
    margin: 0 auto;
    border:1px solid #aaa;
}
#controller {
    margin:0 auto;
    .op_btn {
        float: right;
        margin:10px 0 0 10px;
        border:2px solid #aaa;
        width: 80px;
        height: 40px;
        line-height: 40px;
        text-align: center;
        font-size: 20px;
        border-radius: 5px;
        cursor: pointer;
        background: #fff;
        font-weight: 700;
        font-family: Microsoft Yahei,Arial;
        &:hover {
            background: #def;
        }
    }
    .clearfix {
        clear: both;
    }
    .color_btn {
        float: left;
        margin:10px 10px 0 0;
        border:5px solid #fff;
        width: 40px;
        height: 40px;
        border-radius: 5px;
        cursor: pointer;
        &:hover {
            border: 5px solid violet;
        }
    }
    .color_btn_selected {
        border:5px solid blueviolet;
    }
    #black_btn {
        background: #000;
    }
    #blue_btn {
        background: blue;
    }
    #green_btn {
        background: green;
    }
    #red_btn {
        background: red;
    }
    #orange_btn {
        background: orange;
    }
    #yellow_btn {
        background: yellow;
    }
}
